1. Field of the Invention
The present invention relates to a tape-shaped recording medium, and an apparatus and a method for processing the medium. More specifically, the present invention is directed to a tape-shaped recording medium capable of being wound regularly, and an apparatus and a method by which the medium is wound regularly.
2. Description of the Related Art
Generally, linear and helical types of magnetic tapes of, for example, 12.7 mm wide are being used widely for external backup recording media for computers, etc. Magnetic tapes of these types are typically handled, with being wound around a tape reel. While a tape is being wound around a tape reel of a winder or a drive, the edge of the tape is sometimes irregular. Especially, when a tape is wound at a high speed, this irregularity is more likely to occur. Such irregularity may damage a tape during transport, or may cause a tape to be curled badly during storage. This badly curled shape is prone to be maintained, and it contributes to the deteriorated running accuracy of a tape in a drive, thereby causing servo tracking errors. Therefore, it is important for a tape to be wound regularly in terms of keeping the high quality level.
On the other hand, it has been known that if a tape has a predetermined laterally curved form, then it less likely to produce the irregularities. This results in the stability of smooth running of a tape, thereby improving the servo tracking property. This technique is disclosed in Japanese Unexamined Patent Application Publication 9-265625.
This predetermined laterally curved shape is recognized by placing the tape on a plat surface and by viewing it from the top. Alternatively, as shown in FIG. 8, it is recognized based on how much a magnetic tape MT deviates from a straight line (reference line) passing through two points on one edge of the tape.
If curved over its whole length by a predetermine amount, then a magnetic tape will be wound regularly. Otherwise, its wound form may become worse. Accordingly, in order to roll up a magnetic tape appropriately, various techniques for curving a magnetic tape by a predetermined amount have been proposed, such as Japanese Unexamined Patent Application Publications 9-138945 and 2004-164808. Herein, the curving amount is expressed by D/L, where L stands for the specific length of a tape, and L stands for a maximum value of an amount where a tape deviates from the reference line.
JP9-138945 discloses a technique for curving magnetic tapes during a tape manufacturing step. Specifically, a magnetic tape is wound around a tapered tape-winding surface. Following this, it is kept standing as it is for a prescribed time. Finally, one side of the wound magnetic tape is expanded so that the tape becomes curved.
JP2004-164808 also discloses a technique for curving magnetic tapes during a tape manufacturing step. In this technique, a magnetic tape is wound around a tapered reel hub. Subsequently, it is left standing as it is at equal to/less than the glass transformation temperature. By this heat exposure, a tape is curved appropriately, thereby ensuring the uniform wound form of a magnetic tape.
Meanwhile, if a surface of a magnetic tape arches in the direction where a magnetic layer is formed, then its durability is improved, thus preventing dropout (data errors) (see Japanese Unexamined Patent Application Publications 5-307731 and 8-63740). Herein, such arching of a tape is called “cupping”.
In a magnetic tape to which a technique of JP9-265625 is applied, its wound form is typically better, as the magnetic tape is curved more sharply. However, on certain conditions, that is, depending on the surface property, edge form, edge rigidity, etc. of a tape, its wound form may be irregular. In this case, it is impossible to provide desired production yields.
Furthermore, according to the technique of JP9-138945, the farther away from a hub a magnetic tape is, the less prominently the shape of the hub acts on the wound form, due to spaces between the wound tape, the thickness difference along the width, or the flash of the tape reel. In addition, the wound form may be affected by the tolerance of the length or the curved shape of a tape, because of the variations in manufacturing quality or the shape of the reel hub.
Moreover, in the technique of JP2004-164808, a magnetic tape is shrunken by a heat treatment, and gaps may be thus formed in the middle of the tape roll. These gaps lead to the irregularity of the tape roll. In this case, the surface of a tape may be damaged, or downstream processes may be impossible to carry out. During the heat treatment, the magnetic tape is fastened and pressed inward, so that the tape becomes wider toward the inside of a roll.
As for cupping of a magnetic tape as in JP5-307731 and JP8-63740, it is known that the sufficient effect is not produced.
Taking the above disadvantages into account, the present invention has been conceived. An object of the present invention is to provide a magnetic tape capable of being wound regularly, and an apparatus and a method by which the tape is wound regularly.